// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains a helper template class used to access bit fields in
// unsigned int_ts.

#ifndef GPU_COMMAND_BUFFER_COMMON_BITFIELD_HELPERS_H_
#define GPU_COMMAND_BUFFER_COMMON_BITFIELD_HELPERS_H_

namespace gpu {

// Bitfield template class, used to access bit fields in unsigned int_ts.
template <int shift, int length>
class BitField {
public:
    static const unsigned int kShift = shift;
    static const unsigned int kLength = length;
    // the following is really (1<<length)-1 but also work for length == 32
    // without compiler warning.
    static const unsigned int kMask = 1U + ((1U << (length - 1)) - 1U) * 2U;

    // Gets the value contained in this field.
    static unsigned int Get(unsigned int container)
    {
        return (container >> kShift) & kMask;
    }

    // Makes a value that can be or-ed into this field.
    static unsigned int MakeValue(unsigned int value)
    {
        return (value & kMask) << kShift;
    }

    // Changes the value of this field.
    static void Set(unsigned int* container, unsigned int field_value)
    {
        *container = (*container & ~(kMask << kShift)) | MakeValue(field_value);
    }
};

} // namespace gpu

#endif // GPU_COMMAND_BUFFER_COMMON_BITFIELD_HELPERS_H_
